1. Field
The subject invention is in the field of methods and apparatus used in the construction, use and maintenance of oil wells. Specifically, it is in the field of methods and apparatus used to maintain oil wells. More specifically, it is in these fields as related to removing products from the wells which interfere with the production of oil by the wells, products such as paraffin and asphaltene.
2. Prior Art
The basic techniques for removal of such products are (1) to raise the temperature of the contents of the well sufficiently to reduce the viscosities of the products enough to allow their mixing with the other products in the well and being carried away with the other products as they are removed from the well; (2) chemical treatment of the well contents to effect removal of the products or alleviate their effects; and (3) combinations of chemical treatment and heating. The U.S. patents listed below are a sampling of the prior art.
______________________________________ 1,462,288 2,836,248 1,525,656 2,881,301 1,646,599 3,045,099 1,681,523 4,289,204 1,835,400 4,836,286 2,561,249 5,247,994 2,639,774 5,265,677 2,644,531 ______________________________________
U.S. Pat. Nos. 1,525,656, 1,835,400 and 2,836,248 show electrically powered heaters intended for use deep in a well. U.S. Pat. No. 4,836,286 discloses method and apparatus for chemically treating well fluids at the output of the well to remove paraffin, asphalt, etc. and returning the treated fluids to the annulus of the well. The most commonly used technique for removing paraffin and asphaltenes is termed "Hot Oiling". In this technique a quantity of oil is heated to between 150.degree. F. and 300.degree. F. and pumped into the annulus of the well, the annulus being the space between the tube of the well and the casing in the well. U.S. Pat. Nos. 1,462,288 and 2,639,774 show methods and apparatus for heating the liquid produced by a well and recirculating all of the output into the well to bring the temperatures of the liquid in the casing and of the tube, casing and formation into which the bore was made to levels high enough to liquefy paraffin, asphaltene, etc. so that they will mix with the liquid and be carried out of the well when all or some of the output is diverted from recirculation into processing and/or storage facilities.
The equipment for each of the prior art methods or systems is permanently installed at each well served.
The prior art methods and equipment for treating wells to remove paraffin, asphaltene and the like is not known to have been or be commercially successful. This is considered to be attributable to the facts that (1) it is not economically feasible to remove paraffin, asphaltene and the like from producing wells by heating the liquid in the well, the tube, the casing and the formation around the well and (2) the equipment used is installed permanently at each well treated even though it is not necessary to continually treat each well, i.e. it is entirely acceptable to treat wells periodically to remove the paraffin, asphaltene and the like. It has also been found that it is not economically feasible to heat the well casing because heating applied to the casing bleeds off to the surrounding formation which has great heat capacity.
As further background of the invention for purposes of this disclosure and, as is well known in the art, an oil well comprises a hole bored into the earth, termed the bore, a tubular casing in the bore, cement between the casing and the bore, a tube enclosed in the casing with space termed the annulus between the outside of the tube and the inside of the casing and a rod which fits closely in the tube and is moved longitudinally in the tube to pump the liquid in the well. Accumulation of paraffin, asphaltene and the like between the rod and tube significantly increases the power required to move the rod in the tube and avoidance of the costs for the increase in power is a major reason for removing the paraffin, asphaltene and the like from the well. In view of these problems with the known prior art, reviewed briefly above, it is recognized that there is a long standing need for a more economical method and related apparatus for removing paraffin asphaltene from producing oil wells without harming the well. Accordingly, the primary objective of the subject invention is to provide such a method. A second objective is that the method and apparatus improve the condition of treated wells.